High frequency iron core



I Feb. 14, 1939.

H. C. RIEPKA HIGH-FREQUENCY IRON coma Filed Sept. 30, 1935v Patented Feb. '14, 1939 2.14am men FREQUENCY mos cone Hellmuth C. Riepka, Berlin-Lichterfelde, Germany, assignor to Steam-Magnesia sellschaft, Berlin-Pankow, Germany Application September 30, 1935, Serial No. 42,825 In Germany October 25, 1934 dclaims.

This invention relates to high frequency iron cores.

It is the object of the invention to provide such cores in an improved form which insures particularly a simple and more economical production thereof.

, ,Cores of this type are, pressed from high frequency iron powder under high pressure, and the thread is as a rule produced during the pressing operation, since subsequent tapping, though possible, is not advisable for various reasons. As in all pressing operations, a burr is formed hereby on the core as a consequence of the separating slit between the top and bottom die and is particularly difllcult to remove, since, corresponding to the thread, it extends in zigzag fashion along both sides of the compressed core.

In the core formed according to the invention these troubles are completely eliminated. This success is attained by suppressing on two opposite sides of the core a part of the thread providing thereby plane flattenings extending up to or into the basic core having the root diameter of the thread and by pressing the core in such a position that the separating slit between the upper and lower die of the pressing tool. and thus the burr produced between them during pressing, is

located along these flattenings whence it can be readily removed. If the flattenings do not cut away only the thread but their planes lie still nearer to the center of the core, it is even possible to leave the burr where it is as then it doesnot project over the circumference of the thread and therefore cannot interfere with the function of the latter.

Although in the new core form a portion of the circumference of the core is not threaded, this is without practical importance, as the thread serves generally only for adjusting the core and has to carry only the weight thereof.

The device for carrying out the pressing process according to the invention is so constructed that the dies, into each of which one-half of the thread is to be-pressed, are only as broad. as the basic core, or slightly less so. Furthermore, by a corresponding construction of the pressing device, slots can be pressed at the same time into the ends of the cores by providing the press mold or the dies with projecting members corresponding to the dimensions of the slots.

By way of example and without restricting the invention to the embodiment shown, one form of the new core and the pressing device for its production is illustrated in the accompanying drawing, in which Figure 1 is a cross section of the pressing device; Fig. 2, a side view thereof; Fig. 3, a view of the die on an enlarged scale; Fig. 4, a view of the high frequency iron core, and Hg. 5, a plan of the core.

mimo- Referring to the drawing, in the press mold a the top die b and the bottom die 0 are movably arranged, each of them bearing one-half of the thread d to be pressed and being only as broad as the diameter of the basic core. It is evident that g burr forming at the points e of the core i during pressing can be easily removed, since merely projections on plane surfaces have to be taken away. If finishing is to be eliminated completely, it is only necessary to make the dies b and c somewhat narrower than the diameter k of the core of the thread. A burr developing at the dividing plane of the compressed iron powder core, may then remain where it is, as it does not interfere any more with the function of the thread.

The width I of the dies band 0 depends on the length of the iron powder cores to be pressed. If slots are to be pressed on the faces thereof, the press lining a is provided with continuous projections a engaging corresponding grooves h on the dies 11 and c. The projections a and grooves h are used also for guiding the dies b and c.

The press mold can be simplified by arranging slot forming projections a on the dies b and c as indicated in Fig. 3. Although this may lead to the formation of burr within the slot, it is not necessary to remove it, as it will be destroyed as a rule during theflrst adjustment of the compressed iron powder core by the screw-driver.

The invention is not limited to the embodiment described and illustrated by way of example in the drawing, but may be varied in different ways without exceeding its scope.

I claim:-

1. A compressed comminuted high frequency core of substantially cylindrical shape provided with a thread, opposite sides of the cylinder being flattened to at least the depth of the thread, said flattenings including the place where the burr is formed in pressing.

2. A compressed comminuted high frequency magnetic core in accordance with claim 1 and in which the flattening is to a depth slightly greater than the depth of the thread so that the burr even if not removed does not interfere with the function of the thread.

3. A compressed comminuted high frequency magnetic core in accordance with claim 1, a slot being provided in at least one of the ends of the core, said slot being parallel with the flattened sides of the cylinder.

4. A compressed comminuted high frequency magnetic core in accordance with claim 1, a slot being provided in at least one of the ends of the core, said slot being parallel with the flattened 

